Mobile communication devices when roaming can perform handovers between different networks. For example, in cellular telecommunication networks, a mobile station can roam from one network to another but, usually, roaming is only permitted between networks for which the subscriber's network provider has a roaming agreement. The mobile station may itself be in range of other networks but it can only roam to those that have a roaming and billing agreement with the network provider.
Mobile communication can be provided by different types of networks. For example, cellular radio telecommunication networks are widely available e.g. complying with the Global System Mobile (GSM) recommendations. GSM networks can handle data as well as voice communication using general packet radio service (GPRS). Recently, broadband services for voice and data have been introduced in so-called third generation (3G) networks according to the ITU-2000 recommendations.
Also, wireless local area networks (WLAN) are used to provide broadband mobile communication with mobile stations such as portable computers or personal digital assistants (PDAs) WLANs comprise a wireless access point that provides a wireless connection to mobile stations within range. The access point may be connected through a core IP network such as the Internet to content providers. Wide area LANs are also proposed for example to provide an information service in the town centre. Smaller area LANs are commercially available to users in coffee shops and other public locations such as airports. Many WLANs operate to IEEE802.11 Recommendations. Typically, WLANs have a wider bandwidth capability than cellular telecommunications networks and the cost of usage to the subscriber may be different from cellular mobile networks.
Hitherto, when a user of a mobile station wishes to roam from e.g. a cellular mobile telecommunications network to a WLAN, communication with the cellular network is terminated and communication with the WLAN is opened. The decision on which network provides the most appropriate communication is determined on the basis of the user's knowledge of the capabilities of the networks concerned. For example, if the user roams into a coffee shop where a WLAN is available that offers a broadband communication over the Internet, it may be more convenient to download content from the Internet through the WLAN.
Sungkwan Jung et al, in “QoS based vertical handoff method between UMTS systems and wireless LAN networks”, Vehicular Technology Conference, 2004, VTC2004-Fall. 2004 IEEE 60th Los Angles, Calif., USA 26-29 Sep. 2004, ISBN: 0-7803-8521-7 describes a handoff method which increases the QoS during handoff.
Similarly, International Patent Application number WO98/322 entitled “Determination of Service Situation in a Packet Radio Network”, describes a method for indicating the prevailing service situation in a packet radio network where several classes of service are determined.
However, the above prior art does not consider increasing QoS to obviate any need for handoff once a handoff has been determined as necessary due to the prevailing QoS. The invention seeks to modify the prevailing QoS if a handoff is indicated as desirable due to the prevailing QoS to prevent handoff from occurring. The present invention thus provides an improved way of deciding whether to make or obviate a network handover.